1. Field of the Invention
The present invention relates to a liquid forced-feed apparatus for feeding a liquid, such as water, fuel, etc., under pressure. The liquid forced-feed apparatus of the present invention is suitable particularly for use in collecting a condensate generated in a steam piping system and feeding this condensate to a boiler or a waste heat recovery system.
2. Description of the Prior Art
Condensate generated in a steam piping system in most cases still has a considerable quantity of stored waste heat. For this reason, it has been a widespread practice to use a condensate recovery system, including a liquid forced-feed apparatus, to recover the condensate and feed it into a boiler or waste heat recovery system. Such a system is designed for the utilization of waste heat from the condensate, thus realizing the effective use of this energy.
The liquid forced-feed apparatus used in prior art condensate recovery systems collects condensate in a hermetic vessel, and introduces a high-pressure working fluid, such as steam, into the hermetic vessel by operating a change-over valve, thereby forcing the condensate from the inside of the hermetic vessel under the pressure of the working fluid.
To ensure high-efficiency operation of the liquid forced-feed apparatus, it is necessary to hold as much condensate as possible in the hermetic vessel and to properly switch the change-over valve. The liquid forced-feed apparatus of the prior art, therefore, generally uses a snap mechanism in order to ensure reliable switching of the change-over valve.
FIG. 1 is a partly sectional perspective view of the type of liquid forced-feed apparatus disclosed in the prior art. The liquid forced-feed apparatus of FIG. 1 has a hermetic vessel 101, and contains a float 120, a changeover valve 130, and a snap mechanism 140. The hermetic vessel 101 is provided with a forced-feed liquid inlet port 102 and a forced-feed liquid discharge port 103 in the vicinity of the bottom, which are fitted with check valves 105 and 106, respectively. The check valve 105 is mounted in a direction such that the condensate is allowed to flow into the hermetic vessel 101, while the check valve 106 is mounted in a direction such that the condensate is allowed to be forced out from the hermetic vessel 101.
In the top of the hermetic vessel 101 are formed a working fluid inlet port 108 and a working fluid discharge port 109, which are fitted with a supply valve 110 and an exhaust valve 111, respectively. The supply valve 110 and the exhaust valve 111, which together form the changeover valve 130, are opened and closed by up and down movement of the valve lifting rods 112 and 113, respectively. The supply valve 110 is opened when the valve lifting rod 112 is up, while the exhaust valve 111 is closed when the valve lifting rod 113 is up. The valve lifting rods 112 and 113 are connected in parallel by a connecting plate 115. The supply valve 110 and the exhaust valve 111 are thus simultaneously opened and closed by moving the connecting plate 115 up and down.
In the prior art liquid forced-feed apparatus of FIG. 1, the forced-feed liquid inlet port 102 is connected to a load of steam via the check valve 105, and the forced-feed liquid discharge port 103 is connected to a boiler, and an apparatus utilizing waste heat, via the check valve 106. The working fluid inlet port 108 is connected to a high-pressure fluid source. When no condensate is present in the hermetic vessel 101, the float 120 is in the lower position and the connecting plate 115 is down, causing the supply valve 110 to close the working fluid inlet port 108 and the exhaust valve 111 to open the working fluid discharge port 109.
If condensate is generated in the load of steam connected to the liquid forced-feed apparatus of FIG. 1, the condensate flows into and gathers in the hermetic vessel 101 via the check valve 105. With an increase in the amount of the condensate, the float 120 rises, causing one end of the arm 118 to rise. If the arm 118 rises over a predetermined level, a snap mechanism 140 turns over to raise the valve stem operating rod 121, thereby raising the connecting plate 115. As the connecting plate 115 rises, the supply valve 110 opens the working fluid inlet port 108 and the exhaust valve 111 closes the working fluid discharge port 109. The pressure in the hermetic vessel 101 then increases, forcing the condensate under pressure out of the forced-feed liquid discharge port 103 via the check valve 106.